Induction system for carbureted two-cycle engines



y 17, 1934- F. G. SHOEMAKER 1,967,069

INDUCTION SYSTEM FOR CARBURETED TWO-CYCLE ENGINES Filed NOV. 21. 1931 2 Sheets-Sheet l July 17, 1934. SHOEMAKER 1,967,069

INDUCTION SYSTEM FOR CARBURETED TWO-CYCLE ENGINES Filed Nov. 21. 1931 2 Sheets-Sheet 2 6/ I 7/ 79 I 71 a a if 5/ 7 7; a; 5

5/ l I I Patented July 17, 1934 V 1,967,069

INDUCTION SYSTEM FOR CARBURETED TWO-CYCLE ENGINES Fred Glen Shoemaker, Ferndale, Mich., assignor to General Motors Research Corporation, Detroit, Mich, a corporation of Delaware Application November 21, 1931, Serial No. 576,546

Claims. (Cl. 123-55) This invention relates to internal combustion Referring by reference characters to the drawengines and particularly to engines operating on ings, numeral 5 is used to designate one of the the two-cycle order. It is further concerned cylinders of a V-type two-cycle engine mounted with an improvement in the mechanism for supon a crankcase 7. The crankshaft is designated 5 plying and for controlling the supply of carburetby numeral 9. At 11 is one of the pistons con-' ed mixture to such an engine. Like other known nected to the crankshaft-by the connecting rod engines, it makes use of a blower to receive the 13. Each cylinder has a head 15 with a compresmixture from the carburetor and deliver it to the sion chamber and spark plugs as usual. At 17 is engine manifold, a manually operable throttle an outlet for exhaust gases. At 19 is a valve 10 valve being used between the discharge of the controlling the inlet of explosive mixture from blower and the engine cylinder or the manifold passages 21 formed in the engine block. The in the case of a multi-cylinder engine. The vavalve is controlled by the usual camshaft and riation in the work to be done isaccomplished, springs, as in prior inventions, by varying the pressure The novel induction unit comprises a casing 35 within the manifold, and this is attained by the 23, a carburetor 25 and a control member 27 M manipulation of the throttle valve located beyond carrying parts to be described, The casing 23 is the outlet of the blower. formed with a main blower chamber 29 contain- With Such an engine it 1185 been found Ileeesing substantially conventional rotors 31 driven sary to ot only cont o the manifold p essu from the crankshaft by a chain 33 as shown in y e t tt e v ve, bu t s o iate t ewit Fig. 1. The carburetor includes a float 35 in automatic mechanism to similarly control the th float bowl and a primary passage 3'7 for air action of the blower in delivering mixture to the which surrounds a fuel jet 39, The o rbureted engine. It is preferred to use e blower. h P- mixture enters the blower chamber 29 at 41 and eration of which consu es bu e comparatively the rotation of the rotors 31 forces the mixture '25 smallp rt of th energy v p d y t engine, from chamber 29 into passages 43 through a t and to work such a blower harder when delivering blgwer t t 45 w th i d ti n it is relatively greater charges and less hard when det d on the engine, the passages 43 livering lesser C a es. municate with the passages 21 in the cylinder An obj ct of my inv o then, is to provide block as clearly indicated by the drawings. It

a simple automatic control of the output of the will be understood that the float bowl to be an blower to the engine whe by h blower 5118411 supplied with fuel from any conveniently located ope a at a p es u o greater than required for source and the fuel from the float bowl supplies the given load a d spe as determined by the the jet so. The casing 23 has passages 47 which throttle. Specifically is 8.11 Object 01' the in" may be located in a plane at right angles to 33- vention to provide a. lay-passage from the blower sages These passages 47 communicate t 9% outlet to its inlet and to make u Of e p i their lower ends with the bottom of chamber 29 loaded Valve thETGin, the Spring load being In" above the 41 They serve as bypass cone eased as the t t Velve is Opened whereby duits to at times return some of the mixture from with closed t r e the Valve may more easily the blower outlet toits inlet. These passages open to circulate a relatively large part oi the have spaced openings 49 t; t top of th as mixture from the blower outlet to its inlet. asing 23. other object a d adv will be understeod The member 27, when positioned as in Fig. i. om th fell-Owing clescrlp covers an opening 51 in. part 23 at the junction of In the drawingsthe induction conduits 43. A throttle valve 53 of Fig. l is a View in elevation, Partly in Vertical circular outline slides in an opening 55 formed in Sect Of a yp two-Cycle engine with which the member 27 which opening 55 is concentric y induction system h s b eeseeietedwith opening 45 from the chamber 29. It will be 2 is a vertical Section through the blewei' seen that the movements of the valve 53 vertid Showing the throttle d a bypass valve. cally open or close the communication from the 59 Fig. 3 is a vertical section at right angles to blower chamber to the passages 43. The valve 53 that of Fig. 2. is guided in opening 55 and it carries a stem 57 Fig. 4. is a view in elevation, partly broken which extends through and is guided by cover away and in section, of the valve members, the member 59. The extremity of stem 57 may be valve members being shown in separated posimanually operated by any convenient means to 55 tions. open and close the throttle valve. The member 27 is further formed with a circular guiding wall 61 concentric with and of the same internal diameter as the opening 55. This wall guides the circular wall of a cup-shaped valve 63. At the junction of the wall of the valve and its base there is a reduced portion which is received in a notched part of the throttle valve 53 as best shown in Fig. 2. An outer spring 67 in abutment with cap 59 is received within and engages the bottom of valve 63. An inner spring 69 also engages the bottom of valve 63 and at its upper end engages a disc 71 carried by the stem 57 at an intermediate point. The bypassages 47 communicate with a passage or space 73 in the member 27, which space is normally closed from communication with the blower outlet 45 by the valve 63. It will be seen that the lifting of the throttle valve is accompanied by a lifting of the bypass valve but without ordinarily opening said valve because of the movement of both valves together. It will also be observed that pressure within chamber 29 may raise the bypass valve away from the throttle valve 53 to permit the discharge of mixture through the bypassages to the entrance of the blower. Fig. 4 shows such a separation of the valves.

At is a disc valve held by a spring 77 to close a supplementary air inlet. The disc 75 has a stem 79 guided in an opening in a boss 81. The supplementary air inlet as shown communicates with the region 73, the passages 47, and the inlet to the blower.

The operation will be briefly described. The fuel from the gas jet and the primary air inlet is forced by the blower through the passages 43 to the engine cylinders when the throttle valve 53 is open. In the event that the engine is turning over at a rate such as to deliver a charge which a completely or partially closed throttle will not accommodate, the bypass valve 63 is lifted by the pressure developed in the blower and the mixture is returned to the blower inlet by way of passages 47. If the conditions are such as to open valve 75, the supplementary supply of air reaches the blower inlet through passages 73 and 47. The springs 67 and 69 jointly operate to hold the bypass valve on its seat on thethrottle valve. As the throttle valve is lifted, the seat 71 of spring 69 is lifted with ittherefore the effort of spring 69 in holding valve 63 on its seat is constant regardless of the extent of opening of the throttle valve 53. The abutment of spring 67 is, however, fixed. Therefore the eifort of this spring to hold the bypass valve seated varies with the opening of the throttle valve. Slight pulsations of the blower pressure may occur without causing opening or closing movements of the bypass valve owing to the extension of the bypass valve for a short distance into the end of the throttle valve. Since one spring operates with a changing pressure and the other with a constant pressure, the springs may be so chosen as to give a resistance to the passage of the mixture through the bypass which increases with throttle opening to any desired degree.

The spring 67 may be made slightlyconical to secure a more rapid increase in the bypass pressure When the throttle is partlyopen the air for the mixgure passing to the engine is supplied to the inle side of the blower, either through the primary air inlet 37 or the auxiliary air valve 75 and the passages 73 and 47 or from both sources. When the blower displacement volume exceeds the volume of mixture passing to the engine, the

excess returns to the blower inlet through the bypass as is obvious. At full throttle the entire blower outlet goes to the engine and the bypass valve is closed. The mixture entering the blower from the gas jet and the primary air inlet may be supplemented by air from the valve 75 and the bypassages 47 leading to the blowerinlet, these sources being conveniently proportioned as by the selection of a spring 77 of predetermined strength to give the desired air and gas ratio in the mixture.

In certain prior constructions it has been proposed to make use of a conduit from the engine side of the throttle to the region of the bypass valve so that the pressure of the inlet manifold may be operable to variably influence the bypass valve. For example, when the throttle is opened the blower pressure tends to open the bypass valve but the conduit from the manifold carries the similar pressure of the manifold to oppositely influence and balance the direct pressure upon the bypass valve from the blower. As a result of these balanced pressures, the spring maintains the bypass valve closed at full throttle as it should. In accordance with my invention no such conduit is used but the pressure of the blower acting to open the bypass valve will so open it at closed throttle but cannot open it at full throttle because the spring load on the bypass valve automatically increases as the throttle opens. I am therefore able to accomplish substantially the results secured by the older arrangement without the provision of the conduit from the manifold to the bypass.

I claim:

1. For use with an engine, a blower, mechanism forming a passage to deliver gaseous mixture from the blower to the engine, a throttle valve in said passage, means affording a return passage from the outlet of the blower to the inlet thereof, a valve in said passage, yielding means operable to close said valve, said valves being operably connected whereby opening movement of the throttle valve increases the tension of said yielding means which functions to close the bypass valve.

2. For use with an engine, a blower, a conduit for delivering fuel from the blower to the engine, a throttle valve in said conduit, a bypass conduit leading from the outlet of the blower to the inlet thereof, a valve in said bypass, a plurality of springs positioned to close said valve, one of said springs having a fixed abutment, the other spring having an abutment movable with the throttle valve. 3. The invention defined by claim 2 together with an auxiliary air inlet having a spring-pressed valve, said auxiliary air inlet communicating with said bypass.

4. For use with an engine, a carburetor, a blower receiving fuel therefrom, a conduit for delivering fuel from the blower to the engine, a throttle valve therein, a bypass from the outlet of the blower to its inlet, a valve in said bypass, said FRED GLEN SHOEMAKER.

lil 

